1. Field of the Invention
The invention relates to a video camera comprising at least a semiconductor image sensor and a rotary sector shutter arranged in a radiation path of the semiconductor image sensor, in which light-dependent charge integration in the semiconductor image sensor is released by applying a control signal thereto.
2. Description Of The Related Art
In video cameras comprising semiconductor image sensors of the charge transfer type, the light-sensitive surface is darkened by means of a rotating sector shutter during the transfer of the charges in a storage member of the image sensor so as to avoid a disturbance of the charge transfer. The rotating sector shutter is further used for reducing the exposure time so as to improve the sharpness when picking up fast moving objects.
In the conventional semiconductor image sensors, the next integration process after the charge transfer is released by means of a control signal. A charge integration in accordance with the incidence of light is thus only possible if this control signal is available and if the light is released by the sector shutter. In the known video cameras, this is utilized for setting exposure times of different lengths. To this end, the phase position of the sector shutter is controlled by means of a suitable control circuit in such a way that the sector shutter has already released the exposure when the integration process is started by means of the control signal.
The integration is ended by rotating the sector shutter. Since the side between a light-transmissive and an opaque sector of the shutter requires a finite time to get from the upper edge to the lower edge of the image, exposure at the lower edge of the image will take longer than exposure at the upper edge. This leads to an amplitude error of the video signal, also referred to as shading.